Rub Vaseline on wax paper.
Stamp into the Vaseline, then stamp on cardstock.
Prepare your ink (either by spritzing watercolor with water, or watering down some reinkers, or smooshing the inkpad cover down into the ink to make a palette on the cover).
Paint over the Vaseline with the watery-ink. (This step smears the Vaseline which continues to "resist" the ink to varying degrees. Notice the background in these samples.)
If desired, stamp with StazOn.